After over a year of use with little issues. Over the last week I have been seeing sync issues on our fire 4K. What I don’t understand is why? No hardware changes. No service change. So by elimination something has changed in the software from Amazon or SD. I don’t know but I assume that Amazon put out betas of the fire firmware to all the app developers? If there is a problem with a Amazon update could SD post a warning. I’m amazed at the consumer good manufactures apparent acceptance of releasing poor code. There seems to be quite a few issues with each software release. I work in the Auto industry. A modern car has millions of lines of code. If the auto industry behaved this way where’d see hundreds of car on the side of the road every day.

PremiumTV has only been available for 2 months. How can you have had used it for over a year?

Are the premium channels using a transport stream (MTS or TS, etc.) or is it using something else? Maybe SiliconDust changed something on the back end to make the quality better, but at the loss of certain synchronization packets?

I'm getting the same issue with my HomeRun Quatro tuner.
It does not matter if it's over the air stations or Premium ones. DVR'd or live.
It happens on the HDHR app, and the Channels App.
It occurs on iOS devices, HDHR or Channels apps.
I have 2 FireTV Cubes and the pennant on wired ethernet (Gigabit Managed Switch) connections.
I have a Mac Tower with HDHR DVR recording setup. It's on wired Gigabit ethernet as well.
I've got a few people in the house that I'm trying to convince this is a good thing.
I'm seeing a lot of these same issues for others.
Hopefully Silicon Dust will read this and get this resolved. (I just love this device!)

As an update, I'm using HDHR-DVR.
The audio sync problem occurs whether the app being used is the native HDHR or Channels.
It's also occurring on OTA stations (without the need for the internet) or Premium channels (needing the internet.)
My TV and laptop devices are all wired to a gigabit network switch.
Mobile devices are the only ones using Wi-Fi.
Wi-Fi is Eero Pro mesh system.
The HDHR-DVR is installed on the last Mac tower before Apple released their short, round, hardly upgradeable design. The recordings (including Live TV) were going to an SSD. Without the DVR service, is there memory in the HDHR hardware for pausing or rewinding live TV?
For my recordings, I've just changed my record location to an external USB 3 drive for space issues. But the solid state drive coupled with the power and RAM of the Mac should have been fine.
Knowing the Mac Natively does not support USB 3, I'm going to add a USB3 card to it.
But knowing a little more about the HDHR hardware will help me troubleshoot from my local side. And hopefully I can help Silicon Dust as well. Given I see this issue with OTA AND Premium Channels, I'm ruling out the connection from the ISP.

I just wanted to throw in my 2 cents worth. I just got an Insignia Fire TV, and I was using the HDHomerun app to watch network television (Kelly Ripa, FWIW) and experienced some laughably awful audio sync issues. Shutting the app down and restarting put it back in sync, but it did not appear to stay there. After restarting, however, the delay never got ridiculous. I have also experienced subtle sync issues on this television watching streaming content using other apps. Reading this thread, FIRE TV seems like a common theme. I know sync issues are common using receivers or soundbars, but I was listening to the Fire TV through its built-in speakers. The TV was connected to my network via wifi. Also, FWIW, I have a small 24" Fire TV in the kitchen. It is a very basic 720 p. television, and (maybe because the screen is much smaller) I have yet to notice any audio sync problems on that television.

I also still use Windows Media Center on my desktop computer, and I have never encountered this problem using WMC.